The present invention is directed toward a safety device and, more particularly, toward a safety device which is intended to prevent a worker who is working in high places such as at the top of a building or on a bridge or the like from being injured in a fall. The device is similarly useful for protecting a worker who may be working in a confined space such as a sewer or tank or the like.
Safety devices of the class to which the present invention pertains and which protect a worker from injury or death caused by falling are generally known. These prior art devices, sometimes referred to as personal fall arrest systems, are used in conjunction with other components such as an anchoring means for the device and a body harness.
Such known devices are generally comprised of a housing which is adapted to be suspended from an elevated structure. A rope or cable winding drum is rotatably mounted in the housing and a spiral spring drives the drum in a direction which continuously tends to wind the cable around the drum. A centrifugally operated brake mechanism responds to an initial fast rotation of the drum in the unwinding direction and brakes the rotation of the drum to prevent further unwinding thereof.
In use, these known safety devices are fixed to a structure such as a building, bridge or the like and the cable extending therefrom is fastened to a worker's belt or harness. Under normal working conditions, i.e. as the worker moves from one place to another, and the rope is drawn in and out of the housing at a reasonable speed, the centrifugal brake is never engaged since the speed of rotation of the drum is relatively slow. Accordingly, the drum rotates freely and the rope is drawn out from or wound on the drum freely. In the event of a fall, however, the rope is drawn out rapidly and the drum is then rotated at a high speed. As a result, the centrifugally operated brake is actuated thereby preventing further rotation of the drum which stops the rope from being drawn out. This arrests the worker's fall and prevents injury or death to the worker which otherwise would occur as a result of the fall.
Previously available safety devices such as those described above have been extremely useful and do prevent serious injury and death to workers. However, they have all suffered from a common deficiency. When a worker has fallen and is being suspended by the rope from the safety device, additional lifting equipment was needed to lift the worker back up to safety.
Because of the elevated locations at which workers using such safety devices are normally working, it was often difficult and time consuming to get the necessary lifting equipment into place. In some situations, it may be possible for a worker to climb to safety. However, it is not uncommon for a worker to be slightly injured during the accident thereby making it difficult for him to lift himself to safety. A similar problem exists if the worker is working in a confined space such as a sewer, tank or the like and must be brought to the surface.
To alleviate the foregoing problem, safety devices have been constructed which incorporate therein a means such as a winch or the like for lifting a worker to safety after he has fallen. Such devices are shown, for example, in U.S. Pat. Nos. 4,489,919 and 4,511,123. In each case, the safety device functions in its normal manner as explained above but in the event of a fall, a normally inoperative lever or crank is engaged and the worker can be raised to safety by slowly turning the drum and winding the rope and cable thereon.
While these two prior patents do describe systems which go a long way to solve the problem of returning a worker to safety, there are many instances when they are still unsatisfactory. Although each of the two described patented systems is capable of lifting a fallen worker back up to the elevation from where he fell, this is not always desirable.
If the safety device is being used by a worker constructing a building, for example, it may not be desirable to lift the fallen worker back up to his initial elevated location. If the worker had been injured during the fall, it could be extremely difficult to then transport the worker back to the ground or to some other lower and safer location. It is desirable, therefore, to be able to either lift or lower a fallen or injured worker to a safer location. The device shown in U.S. Pat. No. 4,511,123 is not capable of lowering a worker. And while U.S. Pat. No. 4,489,919 does suggest such a system, it is wholly inadequate since it relies on the braking system of the safety device to prevent a fall while lowering rather than providing an additional braking means. This can be particularly dangerous if control of the handle is lost when the worker is only several feet from the ground since he may sustain further injuries before the main brake is activated.